Pumps of this type are known, for example, from DE 198 04 260 C2, DE 200 10 494 U1, DE 298 22 365 U1, DE 199 50 257 A1, DE 697 29 108 T2, DE 102 41 753 C1, DE 195 34 774 A, DE 198 55 898 C2 and DD 279 043 A1. They are used to convey viscous and aggressive media which may also contain solid particles. Eccentric single-rotor screw pumps have a very broad range of applications which extends from the food industry to the building industry and are distinguished by a very simple construction with few moving parts.
Aside from the drive and connecting parts, they essentially consist of a stator and a rotor. The stator has a casing which is lined with an elastomer while leaving an axially continuous, central, spiral cavity. The cavity serves to accommodate the rotor which is also coiled, the helix of the stator being a pitch larger than that of the rotor. When the rotor is actuated, progressive chambers, in which the material to be conveyed is conveyed from the intake side to the pressure side, form between its outer contour and the inner contour of the elastomer lining.
The casing of the stator can be smooth-walled, as found e.g. in DE 195 34 774 A1, or also follow the winding of the elastomer lining, as disclosed e.g. in DE 198 04 260 C2. The latter design has the advantage that the elastomer lining has a uniform wall thickness, as a result of which the pressing with the rotor seen over the length of the stator becomes uniform. However, this advantage is obtained at a higher production cost for the stator casing.
A stator for an eccentric single-rotor screw pump is known from DE 102 41 753 C1 which is composed of several segments that extend in axial direction. The longitudinal edges of these segments are thereby formed in such a way that they engage in a form-locking manner, e.g. in the manner of a groove and tongue joint, and are movable against one another. By combining these segments, the diameter of the stator can be varied, as a result of which additional construction and tool costs are not incurred for every new pump size or group of pump sizes.
The pressure that can be obtained with an eccentric single-rotor screw pump on the pressure side is dependent on the number of stages and with that also on the length of the stator. In principle, the stators can be produced in one piece in all required lengths. However, the tool and production costs also increase with increasing length of the stator since larger machines must generally be used. As a result, it has also already been proposed (DE 19 85 861 U1) to arrange stators in a row in that they adjoin one another directly, i.e. without a gap, and are held together with connecting rods. A sealing ring is pushed over each joint abutment, said sealing ring having peripherally extending grooves on both sides of the joint abutment, said grooves serving to accommodate seals and centering both adjoining stators in the middle. This solution has the disadvantage that the seal provided between two stators does not withstand higher pressures.